Space Station Meteor Shower

The crew of the International Space Station enjoyed
a unique view of the 2001 Leonid meteor storm.

May
17, 2002: "It looked like we were seeing UFOs approaching
the earth flying in formation, three or four at a time,"
recalls astronaut Frank Culbertson. "There were hundreds
per minute going beneath us, really spectacular!"

That was last November, and Culbertson, then the commander
of the International Space Station (ISS), was watching the 2001
Leonid meteor storm. No UFOs, just lots and lots of "shooting
stars."

News reports had warned sky watchers in advance: On Nov. 18,
2001, Earth was due to plow through a minefield of debris shed
by Comet Tempel-Tuttle. Innumerable bits of comet dust would
become meteors when they hit Earth's atmosphere at 144,000 mph.
Experts predicted an unforgettable display ... and it came.

Millions of people saw the show, but only three of them
-- the ones on board the space station -- saw it from above.
"We had to look down to see the meteors," says Culbertson.
"That's because the atmosphere (where comet dust burns up)
is below the station."

"A typical Leonid disintegrates about 100 km above Earth's
surface," explains NASA scientist Rob Suggs. "The ISS
is much higher than that. The station (like the space shuttle)
orbits our planet at an altitude of about 350 km." Suggs
is the leader of the Space Environments group at the Marshall
Space Flight Center; he helped organize the crew's observations
of the Leonids.

"I had seen [meteors] on shuttle flights before,"
continued Culbertson, "but when the Leonids happened it
was supposed to be one of the best showers in a long time, so
we stayed up late to see them. Mikhail Tyurin and I were inside
the Pirs docking compartment, which had the darkest windows."
(Pirs is one of the Russian-built parts of the ISS; it
serves as a docking port for visiting Progress supply ships and
Soyuz crew capsules.)

Gazing at the nightside of the earth below, they spotted so
many meteors that they soon lost count of all the flashes. Culbertson
used a handheld video camera to film parts of the storm, but
it wasn't designed for low-light photography. The best images
were the ones Culbertson saw using nothing but his eyes: "The
storm was pretty spectacular," he said again.

Left: This still frame from a video captured
by Frank Culbertson during the 2001 Leonid meteor shower shows
a distant sunrise (the wedged-shaped glow) and a Leonid fireball
exploding in the foreground. Click on the image for a 15
second movie.

Leonid meteors come from the direction of the constellation
Leo -- hence the name Leonids. At one point during the
storm, the space station passed almost directly between Leo (above)
and the Earth (below). Peering out the window, Culbertson could
see meteoroids disintegrating directly underneath the station.
"Then's when you start thinking," he recalled, "they're
coming right by us! It's like being in the middle of a hailstorm."

"We didn't have any damage, but Vladamir (Dezhurov) said
he heard some little pings on the outside of the module,"
Culbertson said with a smile. "I'm not sure if he really
did ... he jokes a lot."

In fact, the station was in little danger. "There are
several hundred different shields protecting the crew and critical
hardware," says Eric Christiansen, the station's Shielding
Subsystem Manager at the Johnson Space Center. "The heavier
shielding typically includes meteoroid/debris blankets. These
are made of a ceramic fabric (NextelTM) backed by
KevlarTM -- the same material found in bullet-proof
vests."

The station's windows are sturdy, too. Each one consists of
at least two panes -- "always with primary and redundant
pressure panes," says Christiansen. "In some cases,
the windows include transparent 'debris panes' specifically designed
to protect them from meteoroid impacts." Others are shielded
(when not in use) by metal shutters and debris blankets.

Although
Leonid meteoroids travel much faster than bullets, the vast majority
of them are microscopic and fragile. They make pretty lights
when they hit Earth's atmosphere -- but that's all. They are
not tough enough to penetrate the station's defenses.

Right: Tiny comet flakes like this are at the heart
of fiery-looking Leonid meteors. This one is only 10 microns
across. [more]

Culbertson was grateful for the protection. "We literally
did see thousands of Leonids all at once. It makes you think
how crowded it is in space sometimes, why it's so important to
have those shields on the outside."

Another Leonid meteor storm is due on Nov. 19, 2002, and forecasters
say it could be even more intense than the one last year. Unfortunately,
a glaring full Moon will diminish the show -- as much for the
crew of the ISS as for sky watchers on the ground below.

Air molecules and aerosols -- that is, water droplets, dust
and smoke -- scatter bright moonlight. Earth's atmosphere literally
glows when the Moon is full. Sky watchers looking up at
the Leonids will see them through a 100-km thick layer of glowing
air. Astronauts looking down at the Leonids will see them
streaking on top of that same glowing layer.

Moonlight will reduce the number of visible Leonids by some
factor between 2 and 5. Even so, that's not necessarily enough
to wipe out a full-fledged Leonid meteor storm. If predictions
are correct, sky watchers -- on Earth and in space -- could see
hundreds or thousands of shooting stars in spite of the glare.

Rob Suggs notes that astronauts have two advantages: "They
see a lot more of the sky than we do from the ground, and they
can't be clouded out!" The crew can probably look forward
to another good show.

Culbertson won't be one of them, though. He's back on the
ground. "I was fortunate to have that perspective,"
he says of the 2001 Leonids from space. After all, it's not every
day you can look down ... and see meteors beneath your feet.

Editor's Note: Frank Culbertson's recollections of
the 2001 Leonid meteor shower were recorded during a speech he
delivered at the Marshall Space Flight Center on March 27, 2002.